It is well established that certain commodities, such as oil and natural gas, are priced according to their BTU (British Thermal Units) content per volume. The more BTU's the oil or gas can produce, the higher its price. Accordingly, the lower the BTU content, the lower its price. Also, it is useful to monitor the output of the source in order to determine the overall worth of the oil or gas well.
In order to determine the BTU content per a given volume of the gas or liquid, it is necessary to analyze the gas or liquid. Ideally, the gas or liquid would be continuously analyzed. This is because the BTU content may and generally does change with time. However, because it is not possible to continuously analyze the gas or liquid, periodic samples are taken and stored within a sample collection cylinder. Once the sample collection cylinder is full, it is taken to a laboratory where the gas or liquid is analyzed for its BTU content. In this manner, an average BTU content is determined for a given period of time upon which pricing of the gas or liquid may be based.
The sample is taken from the oil or gas pipeline by a sampler or sample pump that is either mounted directly onto the pipeline or is remote therefrom. In the case of direct mount, a probe generally extends into the pipeline for sample collection with the sampler timed to periodically receive and store the sample within the sample cylinder. In the case of a remote mount, a line or conduit extends into the pipeline and communicates with the sampler to provide the necessary sample.
In the prior art the sample collection cylinder was remote from the pipeline and sampler and exposed to the elements. This arrangement facilitated the exchange of sample collection cylinders when the old sample collection cylinder was full. However, it has been found that for optimum sample storage within the sample collection cylinder, the sample collection cylinder should be maintained at or near the same temperature as the liquid or gas flowing within the pipeline.
By maintaining the sample collection cylinder at or near the same temperature as the flowing gas or liquid, the volume of the sample received in the sample collection cylinder will be the same volume as sampled. Further the total sample volume of the sample collection cylinder will remain nearly constant.
In the prior art it is known to enclose the sampler or sample pump within a housing in order to alleviate the possibility of contaminants entering and mixing with the sample, as well as protect the sampler or sample pump itself from the elements. The other components of the sampling apparatus are remote from the pipeline and exposed to the elements.
It would thus be advantageous to have the sample collection cylinder and its eventual contents to be maintained at essentially the same temperature as the gas or liquid flowing within the pipeline.